WASHINGTON – The former child actor, whose six episodes as Cousin Oliver on “The Brady Bunch” in 1974 remain forever linked to the popular situation comedy’s downfall, is getting the last laugh – a hit television show.

When 9-year-old Robbie Rist joined “The Brady Bunch” midway through its fifth season, he had no idea the show was about to end, or that his character’s involvement would become synonymous with what often occurs when a child actor is interjected into an established cast.

“At the time, this was like just another gig. (“The Brady Bunch”) was a popular show, but it wasn’t this level of cultural significance – that didn’t happen until it went into syndication,” says Rist, in a phone interview from Los Angeles.

Rist says he wasn’t told at the time that his character – the nephew of Carol Brady, the TV family’s mother – was introduced because network officials felt the rest of the cast had become too old by TV kid standards.

“I was just happy to be working,” says Rist. “It was all good.”

But six episodes in, with “Sanford and Son” beating “The Brady Bunch” in the ratings, the plug was pulled.

“I didn’t even know it got canceled,” says Rist. “We found out it got canceled just because we didn’t go back to work.”

Rist says the backlash didn’t begin immediately, but it came with a name – Cousin Oliver Syndrome. Rist believes the phrase was coined on a website called “Jump the Shark,” named for an episode of “Happy Days.”

“It was a sign the show was over when Fonzie had to jump over a shark tank,” Rist recalls. “There was a page on the site called New Kid in Town, and it was about all the kids that were brought into television shows, like Little Ricky for